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Active Galactic Nuclei with Starbursts: Sources for Ultra High Energy Cosmic Rays  [PDF]
P. L. Biermann,J. K. Becker,L. Caramete,L. A. Gergely,I. C. Maris,A. Meli,V. de Souza,T. Stanev
Physics , 2009, DOI: 10.1142/S0218271809015369
Abstract: Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst in the radio galaxy Cen A pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across most of the sky.
Investigation of the Galactic Magnetic Field with Ultra-High Energy Cosmic Rays  [PDF]
Martin Erdmann,Gero Mueller,Martin Urban
Physics , 2015,
Abstract: We present a method to correct for deflections of ultra-high energy cosmic rays in the galactic magnetic field. We perform these corrections by simulating the expected arrival directions of protons using a parameterization of the field derived from Faraday rotation and synchrotron emission measurements. To evaluate the method we introduce a simulated astrophysical scenario and two observables designed for testing cosmic ray deflections. We show that protons can be identified by taking advantage of the galactic magnetic field pattern. Consequently, cosmic ray deflection in the galactic field can be verified experimentally. The method also enables searches for directional correlations of cosmic rays with source candidates.
Ultra High Energy Particles Propagation and the Transition from Galactic to Extra-Galactic Cosmic Rays  [PDF]
Roberto Aloisio
Physics , 2012, DOI: 10.1051/epjconf/20135306001
Abstract: We discuss the basic features of the propagation of Ultra High Energy Cosmic Rays in astrophysical backgrounds, comparing two alternative computation schemes to compute the expected fluxes. We also discuss the issue of the transition among galactic and extra-galactic cosmic rays using theoretical results on fluxes to compare different models.
Ultra High Energy Cosmic Rays from decays of Holeums in Galactic Halos  [PDF]
Abhijit L. Chavda,L. K. Chavda
Physics , 2008,
Abstract: Stable, quantized gravitational bound states of primordial black holes called Holeums could have been produced in the early universe and could be a component of the Super Heavy Dark Matter (SHDM) present in galactic halos. We show that Holeums of masses of the order of 10**13 to 10**14 GeV and above are stable enough to survive in the present-day universe. We identify such Holeums as promising candidates for the SHDM "X-particle" and show that the decay of such Holeums by pressure ionization can give rise to cosmic rays of all observed energies, including Ultra High Energy Cosmic Rays (UHECR). The absence of the GZK cut-off is explained by the galactic halo origin of the UHECR. We predict that the cosmic rays are a manifestation of the end-stage Hawking radiation burst of the primordial black holes (PBH) liberated by the ionization of Holeums. Antimatter detected in cosmic rays could be a signature of their Holeum origin.
Signatures of galactic magnetic lensing upon ultra high energy cosmic rays  [PDF]
Diego Harari,Silvia Mollerach,Esteban Roulet
Physics , 2000, DOI: 10.1088/1126-6708/2000/02/035
Abstract: We analyse several implications of lensing by the regular component of the galactic magnetic field upon the observed properties of ultra high energy cosmic rays. Magnetic fields deflect cosmic ray trajectories, causing flux (de)magnification, formation of multiple images of a single source, and time delays. We derive the energy dependence of these effects near the caustics at which the flux amplification of a point source diverges. We show that the large magnification of images around caustics leads to an amplification bias, which can make them dominate the flux in some energy ranges. We argue that clustering in the arrival directions of UHECRs of comparable energy may be due to magnetic lensing around caustics. We show that magnetic lensing can also significantly alter the observed composition of cosmic rays at the highest energies. We also show that the time delay between events from a single image may monotonically decrease with decreasing energy in the neighborhood of a caustic, opposite to its behaviour in normal regions.
Active Galactic Nuclei: Sources for ultra high energy cosmic rays?
Biermann, P. L.;Becker, J. K.;Caramete, L.;Curutiu, A.;Engel, R.;Falcke, H.;Gergely, L. A.;Isar, P. G.;Maris, I. C.;Meli, A.;Kampert, K. -H.;Stanev, T.;Tascau, O.;Zier, C.
High Energy Physics - Phenomenology , 2008, DOI: 10.1016/j.nuclphysbps.2009.03.069
Abstract: The origin of ultra high energy cosmic rays promises to lead us to a deeper understanding of the structure of matter. This is possible through the study of particle collisions at center-of-mass energies in interactions far larger than anything possible with the Large Hadron Collider, albeit at the substantial cost of no control over the sources and interaction sites. For the extreme energies we have to identify and understand the sources first, before trying to use them as physics laboratories. Here we describe the current stage of this exploration. The most promising contenders as sources are radio galaxies and gamma ray bursts. The sky distribution of observed events yields a hint favoring radio galaxies. Key in this quest are the intergalactic and galactic magnetic fields, whose strength and structure are not yet fully understood. Current data and statistics do not yet allow a final judgment. We outline how we may progress in the near future.
Galactic Ultra-High-Energy Cosmic Rays  [PDF]
A. V. Olinto,R. I. Epstein,P. Blasi
Physics , 1999,
Abstract: The absence of the expected GZK cutoff strongly challenges the notion that the highest-energy cosmic rays are of distant extragalactic origin. We discuss the possibility that these ultra-high-energy events originate in our Galaxy and propose that they may be due to iron nuclei accelerated from young, strongly magnetic neutron stars. Newly formed pulsars accelerate ions from their surface through relativistic MHD winds. We find that pulsars whose initial spin periods are shorter than $\sim 4 (B_S/10^{13}{\rm G})$ ms, where $B_S$ is the surface magnetic field, can accelerate iron ions to greater than $10^{20} eV$. These ions can pass through the remnant of the supernova explosion that produced the pulsar without suffering significant spallation reactions. Depending on the structure of the galactic magnetic field, the trajectories of the iron ions from galactic sources can be consistent with the observed arrival directions of the highest energy events.
The Galactic magnetic field and propagation of ultra-high energy cosmic rays  [PDF]
Michael Prouza,Radomir Smida
Physics , 2003, DOI: 10.1051/0004-6361:20031281
Abstract: The puzzle of ultra-high energy cosmic rays (UHECRs) still remains unresolved. With the progress in preparation of next generation experiments (AUGER, EUSO, OWL) grows also the importance of directional analysis of existing and future events. The Galactic magnetic field (GMF) plays the key role in source identification even in this energy range. We first analyze current status of our experimental and theoretical knowledge about GMF and introduce complex up-to-date model of GMF. Then we present two examples of simple applications of influence of GMF on UHECR propagation. Both examples are based on Lorentz equation solution. The first one is basic directional analysis of the incident directions of UHECRs and the second one is a simulation of a change of chemical composition of CRs in the energy range 10^13 - 10^19 eV. The results of these simple analyses are surprisingly rich - e.g. the rates of particle escape from the Galaxy or the amplifications of particle flux in specific directions.
Ultra high energy cosmic rays and the large scale structure of the galactic magnetic field  [PDF]
Todor Stanev
Physics , 1996, DOI: 10.1086/303866
Abstract: We study the deflection of ultra high energy cosmic ray protons in different models of the regular galactic magnetic field. Such particles have gyroradii well in excess of 1 kpc and their propagation in the galaxy reflects only the large scale structure of the galactic magnetic field. A future large experimental statistics of cosmic rays of energy above 10$^{19}$ eV could be used for a study of the large scale structure of the galactic magnetic field if such cosmic rays are indeed charged nuclei accelerated at powerful astrophysical objects and if the distribution of their sources is not fully isotropic.
Cosmic Ray Origin: Lessons from Ultra-High-Energy Cosmic Rays and the Galactic/Extragalactic Transition  [PDF]
Etienne Parizot
Physics , 2014, DOI: 10.1016/j.nuclphysbps.2014.10.023
Abstract: We examine the question of the origin of the Galactic cosmic-rays (GCRs) in the light of the data available at the highest energy end of the spectrum. We argue that the data of the Pierre Auger Observatory and of the KASCADE-Grande experiment suggest that the transition between the Galactic and the extragalactic components takes place at the energy of the ankle in the all-particle cosmic-ray spectrum, and at an energy of the order of $10^{17}$ eV for protons. Such a high energy for Galactic protons appears difficult to reconcile with the general view that GCRs are accelerated by the standard diffusive shock acceleration process at the forward shock of individual supernova remnants (SNRs). We also review various difficulties of the standard SNR-GCR connection, related to the evolution of the light element abundances and to significant isotopic anomalies. We point out that most of the power injected by the supernovae in the Galaxy is actually released inside superbubbles, which may thus play an important role in the origin of cosmic-rays, and could solve some persistent problems of the standard SNR-GCR scenario in a rather natural way.
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